Leptalpheus azuero, Anker, Arthur, 2011

Anker, Arthur, 2011, Six new species and three new records of infaunal alpheid shrimps from the genera Leptalpheus Williams, 1965 and Fenneralpheus Felder & Manning, 1986 (Crustacea, Decapoda), Zootaxa 3041, pp. 1-38 : 9-12

Leptalpheus azuero sp. nov.

Figs. 5–7

Type material. Holotype: female (cl 2.8 mm), MNHN-IU-2011-5239, Panama, Pacific coast, Chitré, Playa El Aguillito, mudflat near mangroves, yabby pump, 0.2–0.5 m at low tide, leg. A. Anker, J.A. Vera Caripe, 0 8.11.2006 [fcn 06-536]. Paratypes: 1 female (cl 2.7 mm), OUMNH.ZC. 2011-06-020, same collection data [fcn 06-537]; 2 females (cl 2.4, 2.6 mm), RMNH D54560, same collection data [fcn 06-526A, 06-526B]; 3 females (cl 2.8–2.9 mm), 1 male (cl 3.7 mm), MNHN-IU-2011-5240, same collection data [fcn 06-528].

Additional material. 1 female (cl 2.6 mm), UP, same collection data as for the type series [fcn 06-534].

Description. Frontal margin of carapace broadly triangular, with short, blunt rostral projection, without orbital crests ( Fig. 5 A, B). Telson widest in proximal third, very slightly tapering distally; dorsal surface with two pairs of strong spiniform setae inserted in deep pits relatively close to lateral margin; posterior margin rounded, with two pairs of spiniform setae at posterolateral angles, lateral much more slender and shorter than mesial ( Fig. 5 C).

Eyestalks with anteromesial margin rounded ( Fig. 5 A). Antennular peduncles rather stout, not greatly flattened dorsoventrally; stylocerite not appressed, exceeding distal margin of first article; ventromesial carina with strong, distally bifid tooth; second article subquadrate, slightly shorter than wide; lateral flagellum with well-developed secondary ramus ( Fig. 5 A, B, D). Antenna with moderately stout basicerite bearing strong distoventral tooth; scaphocerite broadly oval, with small, acute distolateral tooth not reaching beyond anterior margin of blade; carpocerite stout, reaching slightly beyond scaphocerite, not reaching beyond end of antennular peduncle ( Fig. 5 B, E). Mouthparts typical for genus. Third maxilliped with moderately elongate, distally subacute lateral plate on coxa ( Fig. 5 F).

Major cheliped slender; ischium unarmed mesially; merus slender, depressed ventrally, with smooth margins; carpus very short, cup-shaped, without large processes distally; chela slender, with palm mostly smooth, depressed ventrally; small field of low tubercles and rugosites present near pollex; fingers about half palm length, not strongly twisted or curved, not gaping when closed; cutting edge of dactylus with large blunt tooth fitting into broad hiatus on pollex, cutting edge of pollex with larger, broadly triangular, proximal tooth and smaller, more narrowly triangular, subdistal tooth, dactylus tip curved upwards, subacute; adhesive disks present ( Fig. 6 A–D). Minor cheliped with ischium unarmed; merus slender, ventrally flattened, with smooth margins; carpus short, cup-shaped; chela very slender, simple, with fingers slightly longer than palm, tips crossing distally; cutting edges minutely rugose ( Fig. 6 E, F).

Second pereiopod with merus slightly shorter than carpus; carpus five-articulated, with article ratio approximately equal to 2.5: 1: 1: 0.8: 2 ( Fig. 5 G). Third and fourth pereiopods similar; third pereiopod relatively slender, compressed; ischium with small spiniform seta on ventrolateral surface; merus almost five times as long as wide; carpus about 0.4 length of merus, with distoventral spiniform seta; propodus with four spiniform setae along ventral margin; dactylus about half as long as propodus, conical, slender, acute distally ( Fig. 5 H). Fifth pereiopod slen- der, not compressed, with three distal rows of setae on propodus.

Male second pleopod with slender appendix masculina only slightly exceeding appendix interna, apex with three stiff setae ( Fig. 5 I). Uropod with lateral lobe of protopod ending in two subacute teeth; exopod with rounded distal margin; diaeresis straight laterally, deeply incised and with blunt tooth near mesial margin ( Fig. 5 J).

Size. The type specimens range from 2.4 to 3.7 mm cl, the largest being a male missing its major cheliped. Colour in life. Semitransparent with small red chromatophores, some forming diffuse transverse bands on the abdomen; antennular and antennal peduncles and tail fan with red chromatophores; chelipeds and walking legs mostly whitish ( Fig. 7 ).

Etymology. Named after Panama’s Azuero Peninsula, on which the type locality of this species is situated; used as a noun in opposition.

Type locality. Panama, Pacific coast, Playa El Aguillito near Chitré.

Distribution. Eastern Pacific: presently known only from the type locality on the Azuero Peninsula of Panama.

Ecology. Shallow sand-mud flat near mangroves, in burrows of unknown hosts; several species of Lepidophthalmus , Upogebia and Axianassa were also collected at this site, but never together with specimens of L. azuero sp. nov. (A. Anker, pers. obs.; Dworschak & Anker, in study).

Remarks. Leptalpheus azuero sp. nov. is morphologically closest to the western Atlantic L. axianassae , differing from the latter by the more produced rostral projection; the presence of a small spiniform seta on the third and fourth pereiopods; and the armature on the major chela fingers, especially the more developed proximal tooth of the pollex and the presence of an additional subdistal tooth near the pollex tip (cf. Fig. 6 C, D and Dworschak & Coelho 1999, figs. 18, 19). Leptalpheus azuero sp. nov. also shows some affinities to the species of the Indo-West Pacific L. pacificus complex, viz. L. pacificus , L. denticulatus and L. dworschaki , but can be separated from these three species by the frontal margin produced anteriorly into a broadly triangular rostral projection (rounded in the other species); the longer stylocerite, exceeding distal margin of the first article of the antennular peduncle (not reaching this margin in the other species); the second article of the antennular peduncle being wider than long (much longer than wide in the other species); and the configuration of teeth on the pollex of the major cheliped (cf. Figs. 5 , 6 and Anker & Marin 2009, figs. 4, 7d, 11d).

Leptalpheus azuero sp. nov. appears to be one of the smallest species of the genus based on the size of the present specimens. The type series consists of a single, apparently adult male (cl 3.7 mm) and several, possibly young or subadult, non-ovigerous females (cl 2.4–2.9 mm). The male is missing its major cheliped, but has a well-developed appendix masculina ( Fig. 5 I) and is otherwise very similar to the females. Four females, including the holotype, have a well-developed, species-diagnostic major cheliped, with very little variation in the armature of the chela fingers ( Fig. 6 D). The type specimens of another eastern Pacific species, L. mexicanus , range from 2.88 mm to 3.54 mm ( Ríos & Carvacho 1983), i.e. size range comparable to the type specimens of L. azuero sp. nov. More sampling of infaunal shrimps is planned at the type locality and other areas of the Pacific coast of Panama to determine the maximum size of L. azuero sp. nov. and also to identify its host or hosts.

Figures

FIGURE 5. Leptalpheus azuero sp. nov.: all except I—paratype, female from Playa El Aguillito, Azuero Peninsula, Pacific coast of Panama (RMNH D 54560); I—paratype, male from the same locality (MNHN-IU- 2011 - 5240): A, frontal region, dorsal view; B, same, lateral view; C, telson, dorsal view; D, ventromesial tooth on first article of antennular peduncle, lateral view; E, scaphocerite, dorsal view; F, third maxilliped, lateral view; G, second pereiopod, lateral view; H, third pereiopod, lateral view; I, appendix masculina and appendix interna, dorsal view; J, uropod, dorsal view (setae omitted).

FIGURE 6. Leptalpheus azuero sp. nov., paratype, female from Playa El Aguillito, Azuero Peninsula, Pacific coast of Panama (RMNH D 54560): A, major cheliped, lateral view; B, same, mesial view; C, same, carpus and chela, lateral view; D, major chela fingers, lateral view; E, minor cheliped, lateral view; F, same, carpus and chela, mesial view.

FIGURE 7. Leptalpheus azuero sp. nov., A, holotype, female from Playa El Aguillito, Azuero Peninsula, Pacific coast of Panama (MNHN-IU- 2011 - 5239), lateral view; B, non-type female from the same locality, dorsal view (UP).